Coagulant for water purification and process for making same.



A.` JACOBSON.

COAGULANT FOR WATER PURIFICATION AND PROCESS FOR MAKING SAME; APPucATwu mw Ara. 21. |914.

1,137,005. Patented Apr. 2T, 1915.

Andrew Jacobson, Smmvto.

We @Wa/9%' i for carrying'out my invention.

ANDREW' JACOBSON, OF COUNCIL BLUFFS, IOWA.

Specification of Letters Patent.

Patented Apr; 27, 1915.

Application filed April 27, 1914. Serial No. 834,855.

To all 'whom it may concern.'

Be it known that I, ANDREW JAcoBsoN, a citizen of the United States, and a resident of Council Bluffs, in the county of Pottawattamie and State 'of Iowa, have invented certain new and useful Improvements in Coagulants for WaterPurification and Processes for Making Same, of-which the followin isa specification. A

/ly invention relates to the art of `water purification and especially to systems -of purification involving the use of coagulants.

It is the object of my invention to provide a coagulant that may be economically employed in such `s ystems or methods of water purification, and to provide a simple and commercially practicable process of preparing such coagulant.

In the accompanying drawing I have illus! trated diagrammatically suita le apparatus Systems of water purification by coagulation may be. defined briefly as systems Wherein there is introduced into the water to be purified certain soluble metal saltsy (designated as coagulants) capable of reacting 'with alkaline materials contained naturally in the water or supplied thereto artificially;

the reaction of the coagulant and alkali 'producing insoluble floeculent 4or gelatinous precipitates consisting of hydrates of .thegmetal basel or bases present the coagulant; said precipitates serving to agglomerate or` agf glutinate the .suspended impurities cong tained in the water; and the precipitate containing said impurities bein subsequently removed from the water' 'y sedimentation or filtration, or, more frequently, by both. j

The efiiciency of any particular substance as a coagulant is, ofcourse, proportional to the quantity of the precipitant hydrate that can be vformed thereby, and the quantity of such hydrate is proportional to the quantity of the metal base contained in the coagulant. The metal salts usually employed as coagulants consist of a metal combinedchemically i with an acid. radical, and the cost of the metal constituent vof the material is-usually very'low as compared with thatof the acid constituent ofthe material. In consequence.

of.',this, it will 'be' apparent that, inthe preparation-.of coagulants, ifqthefamount of metal therein can be lincreased lwithout .a proportionate increase in the acid constituent of the material, the effectiveness'of the material .as a coagulant will lbe increased without a corresponding increase inthe cost of the material.

With the foregoing considerations in view my invention may be regarded as a means ,0 increasing the amount ofl the metallic constituents of a coagulant without porpor tionally increasing the amountot the acid constituents thereof; and rthe l method ,of practising the inventionI mayhbe stated as subjecting a metal to the actonAof, as oluble 'salt lof another metal to Vproducena; correspending salt of the first metal together with a s'oluble basic saltofthesecond metal.

The invention will,be better understood by considering a specific application of it, rather than the foregoing general statement thereof.

' One ofthe materials most cpxnmonlynsed as a coagulant is sulfate of.`aluminium,vof

tions stated, a part of the acid constituent of the aluminium sulfate combines withlfthe.

which the chemical com ositionis'egrprgssed 4)? .A Solution of other metalto form a sulfate thereoffwhile vthe aluminium sulfate is reducedv 0r decomposed to form a basic lsulfate havingl the formula, Al2 (OH) 2 S001. I I Ihe reaction of aluminium sulfate withv metallic ironmaybe expressed as follows:

Alrsoo. .Fe 211,0 Ai,(om.(so.),4 reso. 2H Aluminium Iron IWater Basic aluminium sulfate sulfativ sulfate gen If the materials remain lin contact .for a sufiiclent time and there is'A an excess of ,iron present, the reactlon wlll continue. until the Ferrous Hydrogreater part of the acid originally combined A with the aluminium has conibinedwijth the iron to form ferrous sulfate;` but in this event there would be formed-an 4insoluble compound of the aluminium.whi c h would not be available for use as a coagulant.

.Hence it is desirable ,to control the 1reaction so that it will conform,siibstantiallyA to the formula-'given above, wherein all -ofthe aluminium remains in a soluble cpmpound, and

wherein the resultant amounts of aluminium and iron in solution are approximately equal, the exact ratio beingV F-e= .97.

The rate at which the reaction proceeds is dependent upon the strength or density of the solution, the temperature, and the duration of contact with the metallic iron. These factors are all controllable and, consequently, the extent to which the reaction is carried may be readily controlled.

In practice the operation would be carried out as follows: A solution of aluminium sulfate of a delnite strength, preferably a 5% to 10% solution, is stored in a tank or suitable receptacle 1 having a capacity sullicient for a days supply. From said tank the solution is drawn off through a constant-flow device, such as a float-controlled valve 2 admitting the solution to a pan 3 so as to maintain a constant level of the liquid in the pan. From the pan-3 the solution is discharged into the reaction-tank 4 in which there is placed a quantitiy of comminut'ed iron, such f as scrap ironrborings,.chips or lings. The

i charged through a pipe 7 reaction-tank sho'wn in the 'drawing has a number of balile-Walls 5 so as to direct the solution with substantial uniformity throughout the mass of iron. There is shown also a perforate steam-pipe 6 disposed at the bottom of the ta ,and through which steam may be admitted thereto so as to heat the materials to the desired temperature which, under average conditions, would be 100 to 120 degrees Fahrenheit. From the reaction-tank the solution, containing iron sulfate and basic aluminium sulfate, is disto be conveyed to and mixed in'suitable proportions with the water to be purified by the coagulant. With the apparatus shown the process is continuous and the solution flows through the apparatus by gravity. 1

In order to compare the eiiciency of the coagulant provided by my invention with.

that of the ordinary coagulant with which the process is commenced, it is necessary to consider the reactions occurring when the coagulant is added` to the Water to be purified.v It is understood, of course, that the Water must contain a suitable alkaline material capable of reacting with the coagulant, and Where such analkali is not normally present in the water it is supplied thereto artificially. A material commonly used for this purpose is lime or lime water, containing calcium hydrate, Ca(OH) 2. Assuming, for simplicity, that calcium hydrate is the only active alkali present, the reaction occurring upon the addition of aluminium sulfate as a coagulant would be expressed by the following:

2Alx 80z +6C8.(QH):" 41(OH)| 503304 Auminium Calcium Aluminium Calcium sulfate hydrate hydrate, sulfate Starting with the' same amount of aluminitaining metallic giron,

Basic aluminium Ferrous Calcium Water Oxygen sulfate sulfate hydrate 4Al(0H)x 2Fe(0H)| 6CaSO Aluminium Ferrie Calcium hydrate hydrate sulfate Considering the atomic weight of aluminium as 27, of oxygen as 16, of hydrogen as ,1 and of iron as 56, and computing the molecular weights of the precipitated hydrates in the reactions expressed by the foregoing formulas, it .will be seen that the eiliciency of the coagulant provided by my invention, as compared with that of the aluminium sulfate-alone, is 526 312. In other words, starting with a `quantity of alum'i/nium sulfate suflicient to produce, when used alone or directly, 312 pounds of coagulant precipitate, I am able to produce by the use of my process 526 pounds of coagulant precipitate (or 312 pounds of aluminium hydrate plus 214 pounds of ferric hydrate); andthe cost of obtaining this additional .effect is merely that of'thelscrap-iron dis` of aluminium having the. composition,

A1,(OH)2 (S002:

3. A coagulant for Water purificatlon, consisting of a salt of one metal anda solublel basic salt of another metal, the rst-named metal being one capable of displacing the second --named metal from its combination with the acid radical of the salt.

4. A coagulant for water purification, consisting of a sulfate of one metal and a soluble basic sulfate of another metal, the firstnamed metal being one capable of displacing the second-named metal from its combination with the sulfuric acid radical, y'

4' l 5. The process of making coagulant for water purification, consisting in passing an aqueous solution of sulfate of aluminium over metallic iron, so that a part ofthe iron is dissolved to Aform iron sulfate, and the sulfate of aluminium is reduced to a soluble basic Asulfate of aluminium.

6. The process of making acoagulant for water purlfication, consisting in forming an aqueous solution of sulfate of aluminium,

passing said solution through a vessel conand controlling the temperature and duration of contact of the water purification, consisting in forming an aqueous solution of sulfate of aluminium, passing said solution through a vessel containing comminuted metallic iron, and controlling the temperature and duration of contact ofthe solution with the iron so that enough of the iron will be dissolved to re- `duce substantially all of the sulfate of aluminium to a soluble basic sulfatel of aluminium.

8. The process of making a coagulant for .water purification, consisting in forming an aqueous solution of a salt of one metal, placing said solution in contact with another metal capable of displacing the first metal from its combination with the acid radical of the salt, and controlling the 'reaction so that only' enough of the second metal will be dissolved to reduce the salt of the firstnamed metal to a soluble basic salt 'of the same.

9. The process of making a coagulant for water purification, consisting in forming an aqueous solution of a sulfate of one metal, placing said solution in contact with another metal capable of displacing the first metal from its combinations with thesulfuric acid radical, S04, and controlling the temperature and duration of contact of the solution with the metal so that only enouth of said metal willl be dissolved to reduce e sulfate of the first metal to a soluble basic sulfate of the same.

10. The process of makingl a coagulant for water purification, co in forming an aqueous solution of sulfate of aluminium, placing said solution in contact with a metal capable of the alu-l minium from its combinations w1 furic acid radical, S04, and controlling the the sulreaction of said solution with said`metal so thatl a sufficient quantity of a sulfate of said Vmetal will be'formed to result in the reduction of the sulfate of aluminium to a soluble basic sulfate of the same.

In testimony whereof I have hereunto subscribed my name in the presence of two ANDREW JACOBSON.

Witn:

JOSEPH Pm, Jr., D. O. Bumm 

